An ancient people living on the steppes of northern Kazakhstan may have been the first to domesticate horses and change the course of human history 5,500 years ago, scientists believe.
Evidence suggests the Botai people not only bred and rode horses, but also drank their milk.
They were taming wild horses 1,000 years earlier than domestication was previously thought to have started in central Asia, and 2,000 years before it came to Europe.
An international team of researchers examined finds from Botai sites east of the Ural Mountains in northern Kazakhstan, a prime habitat for wild horses thousands of years ago.
Bone remains showed that the animals were similar in shape to later Bronze Age domestic horses, but different from wild horses from the same region.
This suggested a planned breeding programme. Horses were chosen for their physical attributes, which were then exaggerated through selective breeding.
Bit markings on the teeth of several Botai horses showed they had been bridled, presumably so they could be ridden.
Finally, the researchers found traces of fats from horse milk in Botai pottery. Mare's milk is still drunk in Kazakhstan, usually being fermented into an alcoholic drinks called "koumiss". The new evidence suggests that the koumiss tradition dates back to the earliest horse herders.
Dr Alan Outram, from the University of Exeter, who led the study reported today in the journal Science, said: "The domestication of horses is known to have had immense social and economic significance, advancing communications, transport, food production and warfare.
"Our findings indicate that horses were being domesticated about 1,000 years earlier than previously thought. This is significant because it changes our understanding of how these early societies developed."
Wild horses were commonly hunted on the Kazakhstan steppes thousands of years ago. This may have set the stage for horse domestication, the researchers believe.
Horses seem to have been domesticated in preference to cattle, sheep and goats.
The animals have the advantage of being able to adapt to severe winters, and they graze all the year round, even in snow. Cattle, sheep and goats, which have to be provided with winter fodder, were a later addition to prehistoric economies in the region.